The present invention relates generally to semiconductor devices, and more particularly to the incorporation of a variable capacitor as an element of an integrated circuit formed on a common semiconductor substrate.
Variable capacitors commonly employ moveable plates that vary the capacitance by varying the amount of overlap of adjacent parallel plates or the distance separating two opposed parallel plates. Integrating such variable capacitors with a moving plate as part of a semiconductor device poses certain problems due to the inherent limitations of semiconductor device fabrication. Examples of variable capacitors integrated on a semiconductor substrate are described in U.S. Pat. Nos. 4,495,820 and 4,672,849, each of which discloses a device that senses changes in distance between a moveable plate and a fixed plate. The present invention departs from the moveable plate approach of these prior patents to achieve a simplified structure and fabrication process for making a semiconductor variable capacitor.